The present invention relates to improvements in apparatus (often called trimming or equalizing devices) which are used in cigarette rod making and like machines to remove the surplus from a continuous stream of tobacco shreds or other comminuted smokable material. More particularly, the invention relates to improvements in apparatus of the type wherein the stream is moved lengthwise by a preferably air-permeable conveyor so that the particles of the stream can be attracted to the conveyor by suction, and wherein the means for removing or segregating the surplus from the remainder of the stream includes one or two driven rotary members whose marginal portions pinch the stream in the middle so that the surplus extends beyond those sides of the members which face away from the conveyor and can be removed by a further rotary member which severs the stream adjacent to the aforementioned sides of the material engaging members. Such apparatus are disclosed, for example, in the aforementioned commonly owned copending applications and also in U.S. Pat. No. 4,210,159 granted July 1, 1980 to Quarenghi. The stream of smokable material is advanced in an elongated channel and is flanked by two parallel sidewalls having openings for portions of the two material engaging members. The further rotary member which severs the stream can be located at a level below the material engaging members. Means is provided to rotate the material engaging members in opposite directions, to drive the conveyor and to rotate the severing member.
The presently preferred severing members resemble paddle wheels and more specifically the impellers of radial blowers. This can be readily seen in FIG. 1 of the patent to Quarenghi. Thus, the severing member has a disc-shaped plate and blades or vanes which extend from one side of the plate and form an annulus. The outer end portions of the vanes knock away portions of the surplus when the conveyor moves the stream lengthwise and the impeller rotates about its own axis.
A drawback of such apparatus is that, at the presently required elevated speed of the stream transporting conveyor, the impeller of the trimming apparatus must be driven at a very high RPM with the result that its vanes actually induce the flow of currents of air which interfere with proper removal of the surplus as well as with the gathering of the removed surplus for reintroduction into the distributor of the cigarette rod making machine. In other words, the surplus removing tool of such apparatus actually performs the function of a blower and thus interferes with orderly removal of the surplus as well as with the transport of removed surplus along a selected path.
Another serious drawback of the just described apparatus is that the vanes of the impeller subject the surplus of smokable material to an excessive comminuting action. This is due to the fact that the rapidly orbiting vanes knock off successive batches of the surplus and thereby sever each particle in the region immediately adjacent to the aforementioned sides of the material engaging members. Consequently, the removed surplus contains an excessive quantity of so-called shorts. If the smokable material contains primarily tobacco shreds, the rapidly rotating vanes sever each and every shred a portion of which extends beyond the engaging members and they also comminute many other shreds in the surplus. Short shreds constitute the inferior fraction of the material which is to be converted into a high-quality stream of tobacco particles or the like.